Acoustically-Enhanced Separators for Aircraft Engines

ABSTRACT

Engine inlets are disclosed that include an intake opening for the ingress of incoming air and acoustic filtration means for generating an acoustic wave that separates or clarifies material from the incoming air. The acoustic filtration means can include at least one ultrasonic transducer with a piezoelectric material configured to be driven to create an acoustic wave, such as a multi-dimensional acoustic wave or angled acoustic wave. Physical filtration means, such as an inertial or vortical separator, can be provided. Other engine inlets are also disclosed in which the acoustic filtration means are located within the physical filtration means. Further disclosed are methods for separating material from air employing acoustic separation means and physical filtration means.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/357,418, filed on Jul. 1, 2016, the disclosure of which ishereby fully incorporated herein by reference in its entirety.

BACKGROUND

They are many different types of filters and separators that areutilized for the separation and filtration of particles that wouldnormally be ingested into the intake of a jet or gas turbine engine.

The goal of these filters and separators is to remove or direct awayparticles of dirt and dust that would be deleterious to both theaspiration of the engine and the erosion and destruction of exposedparts in the engine.

Vortical and inertial separators achieve some success in the removal oflarge particles, but fail to remove finer dust particles that may damageand choke an air aspirating engine. Physical filters are able to removemost of the particles that would normally be ingested into an airaspirating engine, but suffer from being clogged during use andeventually shutting off the air flow into the air aspirating engine.

It would therefore be desirable to remove both small and large particlesfrom air prior to intake into an air aspirating engine, such as a jet orgas turbine engine, without causing diminished airflow or damage fromsmall particles into the air aspirated engine.

BRIEF SUMMARY

The present disclosure provides methods and devices that utilizeacoustics to assist separators (e.g., vortical and inertial separators)with the separation of fine particles that would normally be ingestedinto a gas turbine or jet engine, such as the engine of an aircraft(e.g., a helicopter or a small airplane). The methods and devices of thepresent disclosure can also be used in a filter “train” including aphysical filter, such that the load on the physical filter is reducedand air flow is improved over time.

Disclosed in example embodiments herein are aircraft engines. In a firstexample embodiment, an engine inlet comprises an intake opening for theingress of incoming air; and acoustic filtration means for generating anacoustic wave that separates or clarifies material from the incomingair.

In certain embodiments, the acoustic filtration means can be locateddownstream of the intake opening.

The first example engine inlet can further comprise physical filtrationmeans for physically separating the material from the incoming air. Incertain embodiments, the physical filtration means can include avortical separator. In particular embodiments, the at least one vorticalseparator can include a plurality of vortical separators arranged inseries. The at least one vortical separator and the acoustic filtrationmeans can be arranged in series with the at least one vortical separatorlocated between the intake opening and the acoustic filtration means.The at least one vortical separator can further be located upstream ofthe acoustic filtration means. In other embodiments, the physicalfiltration means can include a barrier filter that collects particlesfrom the incoming air. In particular embodiments, the engine inlet canfurther comprise an intake manifold located about an inner wall of theengine inlet between the acoustic filtration means and the physicalfiltration means, the intake manifold configured to receive the materialthat is physically separated from the incoming air by the physicalfiltration means.

Further yet, the first example engine inlet can comprise an intakeappendage, wherein the acoustic filtration means is located upstream ofthe intake opening between the intake opening and the inlet appendage.

In a second example embodiment, an engine inlet comprises physicalfiltration means for physically separating material from incoming air;and acoustic filtration means for generating an acoustic wave configuredto separate or clarify material from incoming air, the acousticfiltration means located within the physical filtration means.

The physical filtration means can be an inertial separator including anair intake that splits into first and second flow streams, the firstflow stream leading to a waste exit and the second flow stream leadingto a clarified air outlet. The acoustic filtration means can be disposedin both of the first and second flow streams.

In a third example embodiment, an engine inlet comprises an intakeopening for the ingress of incoming air; and a vortical separatorincluding blades configured to vibrate at a frequency that generates anacoustic wave that urges the material to an inner wall of the engineinlet.

Further disclosed herein is a method for separating material from air.In an example embodiment, the method comprises receiving incoming airvia an intake opening of an engine inlet; and employing acousticseparation means to generate an acoustic wave that separates orclarifies material from the incoming air. In certain embodiments, themethod can further comprise employing physical filtration means tophysically separate the material from the incoming air

In each example embodiment, the acoustic filtration means can include atleast one ultrasonic transducer including a piezoelectric material thatis configured to be driven to create an acoustic wave in the engineinlet. The at least one ultrasonic transducer can be configured to bedriven to create a multi-dimensional acoustic wave. The at least oneultrasonic transducer can also be configured to be driven to create anangled acoustic wave oriented at an acute angle relative to thedirection of mean flow through the engine inlet. In particularembodiments, the at least one ultrasonic transducer can include aplurality of ultrasonic transducers disposed about an inner wall of theengine inlet.

In other embodiments, the acoustic filtration means can include a movingrotor configured to rotate relative to a stationary rotor to create apulsed acoustic wave.

The example engine inlets can be part of the engine for an aircraft(e.g., a helicopter).

These and other non-limiting characteristics are more particularlydescribed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the example embodimentsdisclosed herein and not for the purposes of limiting the same.

FIG. 1 is a cross-sectional illustration of an example engine inlet foran air aspirating engine utilizing dual vortical separators and aplurality of ultrasonic transducers.

FIG. 2 is a cross-sectional illustration of an inertial separatorincorporating acoustic filtration means.

FIG. 3 is a cross-sectional illustration of an example engine inlet foran air aspirating engine utilizing a vortical separator and a pair ofrotors for acoustic filtration.

FIG. 4 is a cross-sectional illustration of an example engine inlet foran air aspirating engine utilizing a vortical separator and acousticfiltration means disposed between an inlet appendage and the vorticalseparator.

FIG. 5 is a cross-sectional illustration of an example engine inlet foran air aspirating engine utilizing a vortical separator having bladesconfigured to vibrate at a frequency that generates an acoustic wavethat urges the material to an inner wall of the engine inlet.

DETAILED DESCRIPTION

The present disclosure may be understood more readily by reference tothe following detailed description of desired embodiments and theexamples included therein. In the following specification and the claimswhich follow, reference will be made to a number of terms which shall bedefined to have the following meanings.

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the embodiments selected for illustration in thedrawings, and are not intended to define or limit the scope of thedisclosure. In the drawings and the following description below, it isto be understood that like numeric designations refer to components oflike function. Furthermore, it should be understood that the drawingsare not to scale.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise.

As used in the specification and in the claims, the term “comprising”may include the embodiments “consisting of” and “consisting essentiallyof.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,”“contain(s),” and variants thereof, as used herein, are intended to beopen-ended transitional phrases, terms, or words that require thepresence of the named components/steps and permit the presence of othercomponents/steps. However, such description should be construed as alsodescribing compositions or processes as “consisting of” and “consistingessentially of” the enumerated components/steps, which allows thepresence of only the named components/steps, along with any impuritiesthat might result therefrom, and excludes other components/steps.

Numerical values should be understood to include numerical values whichare the same when reduced to the same number of significant figures andnumerical values which differ from the stated value by less than theexperimental error of conventional measurement technique of the typedescribed in the present application to determine the value.

All ranges disclosed herein are inclusive of the recited endpoint andindependently combinable (for example, the range of “from 2 grams to 10grams” is inclusive of the endpoints, 2 grams and 10 grams, and all theintermediate values).

A value modified by a term or terms, such as “about” and“substantially,” may not be limited to the precise value specified. Theapproximating language may correspond to the precision of an instrumentfor measuring the value. The modifier “about” should also be consideredas disclosing the range defined by the absolute values of the twoendpoints. For example, the expression “from about 2 to about 4” alsodiscloses the range “from 2 to 4.”

It should be noted that some of the terms used herein may be relativeterms. For example, the terms “upper” and “lower” are relative to eachother in location, e.g. an upper component is located at a higherelevation than a lower component in a given orientation, but these termscan change if the device is flipped. The terms “inlet” and “outlet” arerelative to a fluid flowing through them with respect to a givenstructure, e.g. a fluid flows through the inlet into the structure andflows through the outlet out of the structure. The terms “upstream” and“downstream” are relative to the direction in which a fluid flowsthrough various components, e.g. the fluid flows through an upstreamcomponent prior to flowing through the downstream component. It shouldbe noted that in a loop, a first component can be described as beingboth upstream of and downstream of a second component.

The terms “horizontal” and “vertical” are used to indicate directionrelative to an absolute reference, e.g. ground level. The terms“upwards” and “downwards” are also relative to an absolute reference; anupwards flow is always against the gravity of the earth.

The present application may refer to “the same order of magnitude.” Twonumbers are of the same order of magnitude if the quotient of the largernumber divided by the smaller number is a value of at least 1 and lessthan 10.

The acoustophoretic technology of the present disclosure employsacoustic standing waves to concentrate and/or separate fine particles.As material (e.g., fine particles) flow past or through the acousticstanding wave(s), the acoustic standing wave(s) traps (retains or holds)the material (e.g., secondary phase materials, including fluids and/orparticles). The scattering of the acoustic field off the materialresults in a three-dimensional acoustic radiation force, which acts as athree-dimensional trapping field.

As the particles are trapped, they can begin to coalesce, clump,aggregate, and/or agglomerate, and grow into larger particle clusters.These particle clusters can be subsequently affected by inertial and/orvortical separation and ejected from the airstream before the airstreamreaches the gas turbine or jet engine.

The acoustic wave may also be utilized to push particles out of the mainair flow, especially smaller particles that do not respond as well toseparation by the vortical separator. An angled acoustic standing wavemay also be utilized to aid in pushing fine materials to the edge of theintake so that such material can be pushed out of the main flow. Theangled acoustic wave may be an acoustic standing wave where the “push”and “pull” of the material in the angled wave acts to separate thematerial from the main incoming air.

In particular embodiments, it may be desirable that the ultrasonictransducer(s) generate a three-dimensional or multi-dimensional acousticstanding wave in the fluid that exerts a lateral force on the suspendedparticles to accompany the axial force so as to increase the particletrapping capabilities of the standing wave. A planar or one-dimensionalacoustic standing wave may provide acoustic forces in the axial or wavepropagation direction. The lateral force in planar or one-dimensionalacoustic wave generation may be two orders of magnitude smaller than theaxial force. The multi-dimensional acoustic standing wave may provide alateral force that is significantly greater than that of the planaracoustic standing wave. For example, the lateral force may be of thesame order of magnitude as the axial force in the multi-dimensionalacoustic standing wave. The three-dimensional acoustic radiation forcegenerated in conjunction with an ultrasonic standing wave is referred toin the present disclosure as a three-dimensional or multi-dimensionalstanding wave.

For three-dimensional acoustic fields, Gor'kov's formulation can be usedto calculate the acoustic radiation force Fac applicable to any soundfield. The primary acoustic radiation force Fac is defined as a functionof a field potential U,

F _(A)=−∇(U)

where the field potential U is defined as

$U = {V_{0}\left\lbrack {{\frac{\langle p^{2}\rangle}{2\rho_{f}c_{f}^{\; 2}}f_{1}} - {\frac{3\rho_{f}{\langle\mu^{2}\rangle}}{4}f_{2}}} \right\rbrack}$

and f₁ and f₂ are the monopole and dipole contributions defined by

$f_{1} = {1 - \frac{1}{{\Lambda\sigma}^{2}}}$$f_{2} = \frac{2\left( {\Lambda - 1} \right)}{{2\Lambda} + 1}$

where p is the acoustic pressure, u is the fluid particle velocity, Λ isthe ratio of particle density ρ_(p) to fluid density ρ_(f), σ is theratio of sound speed c_(p) through the particle to fluid sound speedc_(f), V₀ is the volume of the particle, and < > indicates timeaveraging over the period of the wave.

The contrast factor of the particles and secondary fluids is based onthe density and speed of sound (compressibility) properties of theparticles and secondary fluid.

Gor'kov gives the time-averaged force on a single, small, compressiblesphere in an arbitrary sound field as:

$F = {- {\nabla\left( {\frac{2}{3}\pi \; {R^{3}\left\lbrack {\frac{\overset{\_}{P^{2}}}{\rho_{f}c_{f}^{\; 2}} - {\frac{\overset{\_}{P^{2}}}{\rho_{p}c_{p}^{\; 2}}\frac{3{\rho_{f}\left( {\rho_{p} - \rho_{f}} \right)}}{{2\rho_{p}} - \rho_{f}}\overset{\_}{v^{2}}}} \right\rbrack}} \right)}}$

where P² is the temporal mean square of the acoustic pressure, ν² is thetemporal mean square of the fluid displacement velocity, and R is theparticle radius.

The pressure and the acoustic displacement velocity are spatiallydependent, such that the above equation can be rewritten for aone-dimensional longitudinal wave in the x-direction as:

$F = {{- \frac{2}{3}}\pi \; R^{3} \times \left( {{\left\lbrack {\frac{1}{\rho_{f}c_{f}^{\; 2}} - \frac{1}{\rho_{p}c_{p}^{\; 2}}} \right\rbrack \frac{\partial\overset{\_}{P^{2}}}{\partial x}} - {\left\lbrack \frac{3{\rho_{f}\left( {\rho_{p} - \rho_{f}} \right)}}{{2\rho_{p}} - \rho_{f}} \right\rbrack \frac{\partial\overset{\_}{v^{2}}}{\partial x}}} \right)}$

Using the equation for adiabatic gases that states

$P = {{- \rho_{f}}c_{f}^{\; 2}\frac{\partial\xi}{\partial x}}$

where P denotes the pressure fluctuations and ξ is the displacement of afluid particle from its equilibrium position, and given a standing waveof the form:

P(x,t)=A cos(ωt−kx)+A cos(ωt+kx)

where P(x,t) denotes the pressure at any given point in space and timealong a single dimension x, ω is the angular frequency of the wave, theamplitude of the standing wave is given by 2×A (A denoting pressureamplitude), and k is the wave number, which is equal to ω/c_(f), it canbe shown that:

${v\left( {x,t} \right)} = {{\frac{A}{\rho_{f}c_{f}}{\cos \left( {{\omega \; t} - {kx}} \right)}} + {\frac{A}{\rho_{f}c_{f}}{\cos \left( {{\omega \; t} + {kx}} \right)}}}$

where v(x,t) denotes the acoustic displacement velocity at any givenpoint in space and time along a single dimension x.

The spatial gradient of the temporal average of the square of acousticpressure P

$\frac{\partial\overset{\_}{P^{2}}}{\partial x} = {{- 2}A^{2}k\mspace{11mu} {\sin \left( {2\; {kx}} \right)}}$

and similarly for the temporal average of the square of the fluiddisplacement velocity:

$\frac{\partial\overset{\_}{{Pv}^{2}}}{\partial x} = {\frac{2A^{2}k}{\rho_{f}^{\; 2}c_{f}^{\; 2}}\mspace{11mu} {\sin \left( {2\; {kx}} \right)}}$

thus, Gor'kov's equation can be reduced to:

F=A ² ωC sin(2kx)

where

$C = {{- \frac{4}{3}}\pi \; R^{3}\frac{{{- 5}\rho_{p}^{2}c_{p}^{\; 2}} + {2\rho_{p}c_{p}^{\; 2}\rho_{f}} + {2\rho_{f}c_{f}^{\; 2}\rho_{p}} + {\rho_{f}^{\; 2}c_{f}^{\; 2}}}{c_{f}^{\; 3}\rho_{f}c_{p}^{\; 2}{\rho_{p}\left( {{2\; \rho_{p}} + \rho_{f}} \right)}}}$

Thus, the displacement for a particle is given.

The use of sound waves may be utilized in a transient (one way) wavethat emanates from a speaker and moves a particle in the direction ofthe propagating wave. Particles may also be trapped in an angledacoustic wave and moved in a direction through the combination of soundenergy and fluid dynamics. An acoustic standing wave may also beutilized to agglomerate particles that can be subsequently separated bya secondary means, such as a vortical or inertial separator. An agent,such as microspheres or a secondary fluid may also be added to the inletto aid in the acoustic separation of fine particles, which may be on theorder of from about 1×10⁻⁶ meters to about 1×10⁻³ meters, for example.

The technology of the present disclosure can be used in an airaspirating engine of an aircraft (e.g., a helicopter). For example, FIG.1 illustrates a first example configuration for an air intake of anengine inlet 100. For purposes of brevity, the first example engineinlet 100 will be described in full detail and any like parts found inthe other embodiments will not be described again and will be referredto using like numbers. The first example engine inlet 100 has an intakeopening 104 at a first end of the inlet 100. The intake opening 104generally permits the ingress of incoming air into the engine inlet 100.At a second end of the inlet opposite the first end thereof an exit 105is located, which generally permits the egress of outgoing air that hasbeen clarified and/or filtered in the engine inlet 100.

Clarification and/or filtration of air in the engine inlet 100 can beachieved by various means. For example, in the first example embodimentillustrated in FIG. 1, the engine inlet 100 includes both physicalfiltration means 102 and acoustic filtration means 101.

As can be seen, in this example embodiment, the physical filtrationmeans 102 includes a pair of vortical separators arranged in series nearthe intake opening 104. The vortical separator(s) generally achievesfiltration of particles from air by density separation using centrifugalforce. In particular, the physical filtration means 102 generallyclarify and/or filter the incoming air of larger material (e.g., largeparticles, such as dirt) and generates vortices that force this largermaterial to an inner wall 107 of the inlet 100 (i.e., along an innerperiphery of the engine inlet) from which the larger material can beremoved via an intake manifold 103 located along the inner wall 107 ofthe inlet 100. In this way, the intake manifold 103 serves to act as aconduit between the interior of the inlet and a waste stream forremoving material filtered by the physical filtration means 102.Although the physical filtration means 102 depicted here are dualvortical separators, it is to be understood that other filtration meanscan be added to, substituted for, or combined with the vorticalseparator(s).

Located downstream (i.e., in the direction of air flow from the intakeopening 104 to the exit 105) of the physical filtration means 102 andthe intake manifold 103 are acoustic separation means 101. As explainedherein, the acoustic filtration means 101 further clarify the incomingair by filtering out fine particles by harnessing the power ofacoustophoresis. In this way, the acoustic filtration means 101 aregenerally capable of filtering material that is smaller in size (e.g.,finer particles, such as dust) than the physical filtration means 102and can thus reduce the load on the physicals filtration means 102 andimprove air flow over time.

As can be seen, in this example embodiment, the acoustic filtrationmeans 101 includes a plurality of ultrasonic transducers disposed aboutthe engine inlet 100 and coupled thereto (e.g., through inner wall 107).In this way, the acoustic filtration means 101 achieve full or near-fullcoverage of the engine inlet 100, which further aids in ensuringsufficient clarification and/or filtration of the incoming air. Asexplained above, the acoustic filtration means 101 can be one or moreultrasonic transducers including a piezoelectric material that isconfigured to be driven to create an acoustic wave in the engine inlet100. To achieve efficient trapping of material in the acoustic wave, thetransducer(s) can be configured to be driven to create amulti-dimensional acoustic wave (including a three-dimensional acousticwave).

Turning now to FIG. 2, an inertial separator 200 is illustrated that isenhanced with the addition of acoustic filtration means 201. Theinertial separator 200 includes an intake 202 at a first end thereof forthe ingress of incoming air. The intake 202 splits into a first flowstream 208 and a second flow stream 209. As can be seen in this exampleembodiment, the acoustic filtration means 201 are located within theinertial separator 200 and are particularly located in both of the firstand second flow streams 208, 209. The first flow stream 208 leads to awaste exit 204 from which material (e.g., particles including dirt anddust) filtered out of the incoming air is dispelled. On the other hand,the second flow stream 209 leads to a clarified air outlet that carriesair that has been filtered and/or clarified of deleterious material toan associated engine.

The acoustic filtration means 201 can include one or more ultrasonictransducers as described herein. Further, the ultrasonic transducer(s)can be configured to be driven to create an angled acoustic waveoriented at an acute angle relative to the direction of mean flowthrough the engine inlet. In this way, as seen in FIG. 2, the ultrasonictransducer(s) disposed within the second flow stream 209 can be angledto urge material toward first flow stream 208, such that the separatedmaterial is dispelled via the waste exit 204 and does not reach theclarified air outlet 203 or the associated engine. The placement of theacoustic filtration means 201 in the internal separator 200 illustratedin FIG. 2 is chosen such that particle material is urged, via acousticpressure, away from the clarified air outlet 203 toward waste exit 204.The internal separator 200 illustrated in FIG. 2 can be used as thephysical filtration means of the inlet or intake of an air aspiratingengine.

FIG. 3 illustrates another example embodiment of an engine inlet. InFIG. 3, example engine inlet 300 again includes both physical filtrationmeans 302 and acoustic filtration means 301. In this example embodiment,the physical filtration means 302 includes a single vortical separatorthat creates inertial forces/vortices that urges material to the innerwall 307 of the engine inlet 300 (e.g., along an inner periphery of theengine inlet) toward an intake manifold 303 located along the inner wall307 of the inlet 300. As previously explained, the intake manifold 303can therefore act as a conduit between the interior of the inlet and awaste stream for removing material filtered by the physical filtrationmeans 302.

Located downstream of the physical filtration means 302 and the intakemanifold 303 is acoustic filtration means 301. In this exampleembodiment, the acoustic filtration means 301 includes a pair of tandemrotors 301 a, 301 b, one configured to remain stationary and the otherconfigured to rotate relative to the stationary rotor. In this example,rotor 301 a rotates and rotor 301 b is stationary, however, in otherexamples, rotor 301 a can be stationary and rotor 301 b can rotate. Asshown in FIG. 3, the stationary rotor 301 b and the moving rotor 301 aare located very close to one another, such that when the moving rotor301 a is rotated relative to the stationary rotor 301 b, a pulsed soundis created (e.g., by creating a pulsed sound that creates an acousticwave). The pulsed sound generates an acoustic wave that can be used tourge material in the incoming air out of the main air flow path (namely,material that passed through or that was not filtered out by thephysical filtration means 302 via the intake manifold 303). While themoving rotor 301 a is depicted upstream of the stationary rotor 301 b inthis example embodiment, the relative locations of the rotors could beswitched as desired. Moving and/or non-moving rotors can be combined invarious combinations and/or in multiples to create the pulsed sound.

Another example engine inlet 400 is illustrated in FIG. 4. In exampleengine inlet 400, an acoustic wave 410 is generated between an inletappendage 406 and acoustic filtration means 401, the acoustic wave 410acting to trap and agglomerate material (e.g., fine particles, such asdust) that is drawn into the engine inlet 400. In this exampleembodiment, the acoustic filtration means 401 includes a moving blade401 a configured to rotate relative to a stationary blade 402 a tocreate a pulsed sound that generates the acoustic wave 410. While themoving blade 401 a is depicted upstream of the stationary blade 401 b inthis example embodiment, the relative locations of the rotors could beswitched as desired. As further seen here, the inlet appendage 406 isgenerally disposed at the intake opening 404 of the engine inletupstream of the acoustic wave 410. The moving blade 401 a of theacoustic filtration means 401 also generally acts as a vorticalseparator and urges material (e.g., large particles, such as dirt) to aninner wall 407 of the engine inlet 400 (i.e., along an inner peripheryof the engine inlet) for removal via the intake manifold 403. Inparticular, the moving blade 401 a of the acoustic filtration means 401acts as a vortical separator by generating vortices that causes theincoming air and material to move in a centrifugal fashion, or to beurged away from a center. The vorticies urge the larger material to theinner wall 407 of the engine inlet 400 toward the intake manifold 403.Further, it is noted that because the acoustic filtration means 401 arelocated upstream of the intake manifold 403 in this example embodiment,the fine material filtered by the acoustic filtration means 401 can beremoved from the engine inlet 400 via the intake manifold 403 beforereaching exit 405.

FIG. 5 illustrates yet another example embodiment of an engine inlet.Example engine inlet 500 includes a vortical separator 502 locatedbetween intake opening 504 and intake manifold 503. The vorticalseparator 502 that incorporates thin blades 511 that are configured tovibrate at a frequency that generates an acoustic wave in the engineinlet 500. As explained herein, the acoustic wave urges material thatenters the engine inlet 500 to an inner wall 507 of the engine inlet 500(e.g., along an inner periphery of the engine inlet). An intake manifold503 is located along the inner wall 507 of the engine inlet 500 and actsas a conduit to a waste stream for removing the filtered material fromthe engine inlet 500.

Other physical filtration means may be used in conjunction with theacoustic filtration means of the present disclosure to assist in theseparation of particles from an air stream. Additional example physicalfiltration means include high efficiency particulate air (HEPA) filters.These filters can, for example, be constructed from nano-fiber fabrics(e.g., made of carbon nanotube fibers) to provide increased surface andsmaller pore size, enabling the capture and separation of finerparticles than conventional filters. As explained above, the use ofacoustic separation means in conjunction with physical filtration meansaids in reducing the load on the physical filtration means, such thatair flow is improved over time.

The present disclosure has been described with reference to exampleembodiments. Modifications and alterations may occur to others uponreading and understanding the preceding detailed description. It isintended that the present disclosure be construed as including all suchmodifications and alterations insofar as they come within the scope ofthe appended claims or the equivalents thereof.

1. An engine inlet, comprising: an intake opening for the ingress ofincoming air; and an acoustic filter for generating an acoustic wavethat separates or clarifies material from the incoming air.
 2. Theengine inlet of claim 1, wherein the acoustic filter is locateddownstream of the intake opening.
 3. The engine inlet of claim 1,wherein the acoustic filter includes at least one ultrasonic transducerincluding a piezoelectric material that is configured to be driven tocreate an acoustic wave in the engine inlet.
 4. The engine inlet ofclaim 3, wherein the at least one ultrasonic transducer includes aplurality of ultrasonic transducers disposed about an inner wall of theengine inlet.
 5. The engine inlet of claim 1, wherein the acousticfilter includes a moving rotor configured to rotate relative to astationary rotor to create a pulsed acoustic wave.
 6. The engine inletof claim 1, further comprising a physical filter for physicallyseparating the material from the incoming air.
 7. The engine inlet ofclaim 6, wherein the physical filter includes at least one vorticalseparator.
 8. The engine inlet of claim 7, wherein the at least onevortical separator and the acoustic filter are arranged in series withthe at least one vortical separator located between the intake openingand the acoustic filtration means.
 9. The engine inlet of claim 8,further comprising an intake manifold located about an inner wall of theengine inlet between the acoustic filter and the physical filter, theintake manifold configured to receive the material that is physicallyseparated from the incoming air by the physical filter.
 10. The engineinlet of claim 1, further comprising an intake appendage, wherein theacoustic filter is located upstream of the intake opening between theintake opening and the inlet appendage.
 11. An aircraft enginecomprising the engine inlet of claim
 1. 12. An engine inlet, comprising:physical filtration means for physically separating material fromincoming air; and acoustic filtration means for generating an acousticwave configured to separate or clarify material from incoming air, theacoustic filtration means located within the physical filtration means.13. The engine inlet of claim 12, wherein the physical filtration meansis an inertial separator including an air intake that splits into firstand second flow streams, the first flow stream leading to a waste exitand the second flow stream leading to a clarified air outlet.
 14. Theengine inlet of claim 13, wherein the acoustic filtration means aredisposed within both of the first and second flow streams.
 15. Theengine inlet of claim 12, wherein the acoustic filtration means includesat least one ultrasonic transducer including a piezoelectric materialthat is configured to be driven to create an acoustic wave in thephysical filtration means.
 16. The engine inlet of claim 12, wherein theat least one ultrasonic transducer is configured to be driven to createa multi-dimensional acoustic wave.
 17. The engine inlet of claim 12,wherein the at least one ultrasonic transducer is configured to bedriven to create an angled acoustic wave oriented at an acute anglerelative to the direction of mean flow through the engine inlet.
 18. Anaircraft engine comprising the engine inlet of claim
 12. 19. A methodfor separating material from a gaseous fluid, comprising: receivingincoming gas via an intake opening of an engine inlet; and employing anacoustic separator to generate an acoustic wave that separates orclarifies material from the incoming air.
 20. The method of claim 19,further comprising employing physical filtration means to physicallyseparate the material from the incoming air.